For decades, researchers have been developing techniques to more accurately and more quickly detect the presence and concentration of a chemical, a gas, a liquid, or other substance. For example, surface plasmon resonance (SPR) is one well-known technique that researches have been using for such detection in a wide variety of areas including, but not limited to, life science research, drug discoveries, electroanalysis and electrochemical applications, environmental science, chemical sensor development, biosensor development, surface characterizations, and food quality, safety, and other analysis. More specifically, in biomedical diagnostics, researchers use SPR to detect antibodies associated with bacteria or a virus to determine the existence of an infection, and researchers also use SPR for gene probes to detect the presence of specific deoxyribonucleic acid (DNA) sequences or ribonucleic acid (RNA) sequences in analytes or other buffer solutions. As another more detailed example, researchers use SPR to detect trace amounts of toxic agents in the air and in water for environmental protection applications or for chemical or biological warfare applications.
Despite the widespread applications for SPR, current SPR techniques still suffer from two major drawbacks: slow response time and limited angular resolution. The first problem prevents the current SPR techniques from detecting fast SPR processes, such as those processes occurring during (a) the initial adsorption of molecules onto surfaces, (b) fast interactions or reactions between surface bound molecules and molecules in solution, and (c) fast conformational changes in adsorbed proteins. The second problem limits the sensitivity of current SPR techniques from detecting small quantities of molecules or small structural or conformational changes in molecules.
In micro-fluidic SPR applications, additional problems typically occur. For example, the background signal often drifts due to temperature and other undesirable fluctuations, which limit the accuracy of the SPR measurement. Additionally, air bubbles and other impurities in the buffer solution also cause many unpredictable changes in the SPR measurement, which prevents the detection of small changes.
Accordingly, a need still exists a detection apparatus and method of detection that overcomes these significant drawbacks.
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